1. Field of the Invention
This invention relates to carbon black adsorbents, and further to a method for the formation of said adsorbents by gasification or partial combustion of liquid and/or solid combustibles, said process resulting in the formation of carbon pellets of separable carbon black.
2. Description of the Prior Art
Carbon black, formed during the gasification or partial combustion of combustibles, is usually washed from the reaction gas stream with water. The resulting suspension of carbon black in the carbon black water is usually characterized by a large specific surface area and other properties typical of activated charcoal.
The recovery of activated charcoal from carbon black has not been previously considered for a number of reasons, among which include:
1. The concentration of the carbon black in the carbon black water represents only about 1 percent by weight. Therefore, recovery of the carbon black by direct methods, such as filtration, is expensive. The separation and drying of the filter cake with a fraction of water of from 80 to 85 percent by weight causes further problems.
2. It is not possible to run a gasification set-up in a way as to guarantee the consistent quality of the carbon black, which is formed as a by-product. As a consequence, it is not possible to use measures which would stabilize the quality of carbon black (such as methods of activation), since, after drying, the carbon black is in the form of a loose powder.
Since the direct recovery of carbon black has until now been economically uninteresting, two methods have been used in order to separate the carbon black from the running water containing it. In these methods, the carbon black is either extracted into oil directly or extracted into oil with a previous petroleum wash. The carbon-oil aggregates or the carbon pellets are then separated and burned. The desirable activated charcoal properties of the carbon black are destroyed, however, through contact of the carbon black with the oil, since the free surface area of the carbon black becomes coated. It is not possible to regenerate the carbon black, such as is known to occur with oil-laden activated charcoal or, at best, it is only possible under limited circumstances. The possibility of obtaining from the aforementioned pellets a useable activated charcoal, therefore, was not heretofore considered.